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Home Energy Efficiency & Insulation


Is more insulation the answer?

At some point you’ve probably heard that more insulation would increase your comfort and decrease your energy bills. We don’t disagree. Your house probably would benefit from more insulation. 

But just throwing insulation up in the attic could do more harm than good! If your energy upgrade isn’t done correctly, you’ll be paying more than you should on your utility bills and possibly even causing damage to your home. If the air sealing is done poorly (or not at all) you’ll lose big money over time. If the insulators carelessly cover up soffit vents or seal the house too tightly, you could end up with ice dams, moisture damage, and more.

In a word…it could make your house SICK. And sick houses lead to sick homeowners!

If your crawl space or attic becomes a breeding ground for mold or other toxic matter, where do you think the spores go? Into your living spaces, of course!  Your home needs proper ventilation, or bad indoor air quality can lead to respiratory issues, headaches, and other health problems. Sick house = sick homeowners. You’re all in it together!

Make sure your contractor tests to verify how much insulation AND ventilation your home needs.

Every home is different. If your contractor doesn’t examine and run tests on your home, they’re just taking a shot in the dark and gambling with your money. They can’t give you what you’re paying for — a safer, more comfortable, and efficient house. It’s that simple.

So have a home energy assessment before you decide where best to invest your money.  And arm yourself with some knowledge before you hire a contractor.

Read below to:

  • Know what to expect from an honest contractor
  • Understand each step of the process
  • Learn best practices, so you know that your house will actually perform better in the long term

First, a definition:

What is R-Value?
R-value is the measure of thermal resistance of an insulating or building material. R-value is expressed as R-11, R-38, etc. The higher the number, the greater the thermal resistance, and the more effective the material is as an insulator. In order for a material to work at its rated R-value, it must be installed correctly.



Once you call us, we will set up an appointment for our Building Analyst, Tom Crapnell, to come to your home. Tom is a Building Performance Institute (BPI) certified Building Analyst and Building Envelope Specialistand has been a carpenter for the last 5 years. He has extensive first-hand knowledge of how elements of a building interact and what needs to be done to ensure occupant comfort, health, and safety. (Our insulation subcontractor, Illiana Insulation, also has BPI-certified staff.)


Insufficient attic insulation Pipe penetration through rigid foam insulation Bathroom pipes penetrating subfloor Unused chase from basement to attic

During this visit, New Prairie will:

    • Measure to obtain square footage and volume of your home
    • Measure quality and quantity of insulation
    • Check to make sure attic air space is vented properly
    • Check for proper venting of bath and kitchen fans
    • Check for intact vapor barrier in crawlspace
    • Identify thermal bypasses (holes) in the “envelope” of the house
    • Check for problems with plumbing, HVAC, or electrical systems (such as knob-and-tube wiring, an old system) that require action before insulation can be installed. (Insulation installed over knob-and-tube can cause a fire.)
    • Check recessed “can” lights for Insulation Contact (IC) rated housings
    • Answer any questions you have
    • And perform the next step, Pre-Testing



Pre-testing is important for setting a base-line for how leaky your home is, and for ensuring safety.  After the work is done, post-testing will show you how much improvement was achieved by comparing the before and after leakage rates. More importantly, it will verify if enough fresh air is flowing into your home to keep it healthy.

CAZ smoke testing Blower door set up in doorway   NPC crew performing CAZ testing

During pre-testing, New Prairie will:

  • Perform a blower door test to determine exactly how leaky your house is. A special fan is set up in your front door, blowing air out. This pulls air through all the small leaks in the envelope of the house. This air flow is measured in cubic feet per minute (CFM).
  • Check gas lines for leaks
  • Check any gas or oil-burning appliances, such as furnaces, hot water heaters, and ovens, for acceptable carbon monoxide levels and proper ventilation

The last two items are known as Combustion Appliance Zone (CAZ) tests, and are designed to ensure occupant safety. They are required before and after insulation and air sealing work to make sure gas or oil-burning appliances are operating and venting safely.



After determining which energy upgrades your home could benefit from, New Prairie will send you a bid outlining your options.



The next steps will vary based on the needs of your home. Your home may not need everything on this list. Generally, New Prairie will come in and do their part first; Illiana Insulation will follow.

In the Attic

Spray foam air sealing of bath fan in attic Proper insulated venting of bath fan through roof Blown-in cellulose insulation in attic

 New Prairie carpenters will:

  • Vent bath and/or kitchen fans to outside with insulated rigid metal pipe, if vents are absent or improperly done
  • Add insulation and weather-stripping to attic hatch

Illiana Insulation will:

  • Move existing insulation to expose recessed lighting (also known as can lighting), wiring, chases, open soffits, and any other holes and penetrations
  • Safely cover and air seal metal can lights, following fire-safety guidelines
  • Apply foam sealer over any holes, cracks, top wall plates, and electrical and plumbing penetrations
  • Smooth existing insulation back down
  • Blow in the required amount of cellulose insulation

In the Basement/Crawl Space

We go the extra mile in your crawlspace. Why? Because you MUST seal vapor out of the crawl if you’re going to seal vents and insulate the rim joist. Otherwise, that vapor will come up through your flooring and you’ll find yourself with mold, structural problems, and health issues.  Both the International Residential Code (IRC) and the Building Performance Institute guidelines insist on appropriate vapor sealing methods — with good reason.

Plastic vapor barrier and caulked battens in crawlspace Plastic vapor barrier sealed around poles in crawlspace Spray foam insulation on crawlspace walls Spray foam insulation in rim joist of basement

New Prairie carpenters will:

  • Clear crawlspace of debris as needed
  • Spread out 12-mil. thick puncture-resistant vapor barrier over the soil or rock, lapping edges up on to the stem walls. Vapor barriers must be continuous, with no open areas. (We use a 12-mil. vapor barrier because our experience with 10-mil. or thinner is that it can be easily punctured after installation.) The 12-mil. is used in radon mitigation and will help guarantee that your crawlspace barrier is not compromised. 
  • Attach edges of plastic to stem walls by nailing strips of wood (battens) over them
  • Seal all seams and penetrations in the vapor barrier with tape and/or caulk
  • Insulate and air-seal crawlspace hatch, if it leads to exterior

Illiana Insulation will:

  • Remove any fiberglass batts from the rim joist area (the area where the house sits on the foundation)
  • Spray foam insulation to R-19 or greater in rim joist area in basement
  • Spray foam insulation to R-19 or greater in rim joist area of crawl-space and down from rim joist to battens, covering entire stem wall, according to building code.

In the Walls

Walls that are empty can be filled with blown-in cellulose insulation. Walls that have fiberglass batts in them can have additional insulation added, but it’s generally not as effective (there tend to be gaps caused by the batts), and may cost a little more. Cellulose can be blown-in from the inside or the outside of your house. Most people opt for outside, since holes have to be made in the wall and patched after the insulation is added.

Blown-in cellulose insulation showing through access holes in kitchen soffit Blown-in cellulose insulation showing through access holes in exterior of house Blown-in cellulose insulation showing through access holes in closet wall Blown-in cellulose insulation in wall cavities

New Prairie will:

  • Perform lead paint safety prep, as needed

Illiana Insulation will:

  • Drill two 2-inch holes in each 16-inch stud cavity, in order to blow in insulation (“Studs” are the upright pieces of wood that make up your walls, and the “stud cavity” is the space between each of your wall studs.)
  • Plug holes with wooden plugs hammered flush with existing siding
  • Blow cellulose into stud cavities to an R-value of R-14 or greater for a 2×4 wall

New Prairie will:

  • Caulk/paint plugs to match house or patch holes in drywall if homeowner requests



The effectiveness of insulating and air sealing is measured by the reduction of air leakage. Depending on what issues we’ve been able to address, New Prairie routinely achieves between 15% and 40% reduction in air leakage. We are aiming to make your home much more efficient and comfortable while still maintaining fresh air ventilation through the house. If your home is too tight, a fresh air ventilator will be needed. You can read more about these systems at the Department of Energy’s website.

Air leakage area in attic before air-sealing Spray foam insulation air-sealing in attic Air leakage area in attic before air sealing Spray foam insulation air-sealing in attic

New Prairie will:

  • Perform a final blower door test to determine how much tighter the house is to guarantee safe indoor air quality
  • Perform another CAZ test if applicable
  • Make sure you’re 100% satisfied

We hope this information helped you understand the appropriate processes for making your home more energy efficient. The techniques above are based on established building science, and will keep your home healthy and sound, as well as save you the most money over time. Don’t settle for less!

To read about the numerous benefits of home energy efficiency, visit
How Well Does Your House Work? 

Call us at 217-344-5131 if you have any questions
or to set up your appointment for an energy assessment.

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To understand air sealing more fully, browse the pictures below (click or double tap them the see them at their largest).